Variable air gap turn compensator



Sept. 28, 1948. H. c. WENDT VARIABLE AIR GAP TURN COMPENSATOR FiledSept. 27, 1946 m 9 In we .m. W? e mu mA IF.

Ha b Patented Sept. 28, 1948 UNITED STATES PATENT OFFICE VARIABLE c3232;OomENsA'roa Harry-G. Wendt, Lynnficld. Mass.,-=-es'signor toGenerallllectric Eco omy, a corporation of New York ApplicationSeptember 27, net-,smn No; 699,904

(CL-1M) l 11.01am- .Thepresent invention relates to lgyroscopesand moreparticularly tea-new and-improved erection system-tor gyroscope of thevertical spin-axis type.

.Gyroscopes of the vertical: spin-axis are used on vehicles such asships: and aircraf-tifor indicating the attitude .of "the vehiclerelative to a horizontal reference plane. Such gyroscopcs arecustomarily provided'with an erectionsystem for processing a gyroscopeto a predetermined reference position relative to the direction ofgravity as indicated by. a ,gravityresponsive precession controldeyicesuch as a pendulum.

Under, certain conditions of operation the pendulum 'is subject tosidewazm acceleration and other forces sothat is does not indicate thetrue vertical andxduring such times it is desirable :to disable theerection system so that the-gyroscope not beprecessed away fromthetruereferenoe position. In connection with .gyroscopes shavingmagnetic erection systems :this has been accomplished heretofore byusingan electromagnet for providing :the magnetic erecting force andprovidingiswitch means for deenergizing the electromagnet whenthependulum does not; tor-some reason, indicate the vertical. Thissystemhasthe disadvantage that a failure of the ielectromagnet duringnormal operation-suchas :might be caused by a power failure .or aninoperative ,control switch, :means that the erection system "becomesinoperative. This may be serious where: a pilot is relying :on theindication provided by theszgyroscope to control an aircraft whenthehorizonqis obscured;

object of theinvention isy-to provide a vertical gyroscope havinga:newandimproved .erechaving a control arrangement such that thesystem:is disabled in the event that the mechanicallimits of the controlpendulum are exceeded.

instill further object of the invention is to provide an improved.gyroscope erection system controlled in such: a way that the: erectionsystem is disabled whenxthe. controlpendulum subjected I .2 to sidewaysacceleration tending to displace the pendulum :from the true vertical.

Further objects and-advantages of the inven tion will becomeapparent andthe invention will be betterunderstood from the following descriptionreferring to the drawing and the features of novelty which characterizethe invention will be pointed out with particularity :in the claimsannexedto and vtorminga, part of this specification.

In the: drawing Rig-:1 isa side elevation view, partly in section, ofuauniversal attitude indicating instrument for aircraft having an erectionsystem embodying the present-invention.

2 is the front view of a portion of the instrument shownin Fig. 1,partly in section, showing certain details :of the erection system.

Fig.v :is a diagrammatic view of the erection system zshowing'rthecircuit connections of the electrical components thereof.

A preferred-embodiment of:my invention is illustratedzin connection witha gyroscopic attitudedndieating instrument of the so-called stabilized'ball or sphere type-used to indicate the pitch and. bank attitudes of anaircraft in flight. Referring to .thedrawing the instrument is shown ascomprising va cylindrical frame I which is adapted to. be inserted "inan opening in the dashpanelof an aircraft so that the front portion 2faces the pilot or other observer. Attached to the front-of, theirame-isa face plate 3 having suitable apertures; {not shown) adapted toreceive mounting 'boltsby means of which the instrument is fastened tothe dash-panel. The face plate 3 has a circular opening 4 through whichrelative roll'and pitch movements of, a movable attitude indicator 5:and arelatively stationary miniature airplane. 6' arepobservedi Theattitude indicator S-iisisupportedonand stabilized by a gyroscopetherotor ibearing-irame-of which is illustrated at 1;, Thegyroscope,whichnmay be of conventional construction, comprises a rotating wheel.(not shownlrmounted in-thebearing frame 1 so as to rotate aboutan:approximately vertical spin axis. The gyroscoperwheelgisdrivenzby asuitable electrical or pneumatic motor housed within the bearing frameI. The attitude indicator 5, which is in theviorm of circular shell,encircles the bearing frame 1. and has-acenter section, preferablyspherical contour, carrying suitable attitude indicating indicia whichmay be, as shown, in the fol-morn series :ofgraduated horizontal lines8.

The pitch attitude of the aircraft is indicated by correspondence: of:one of the calibrated lines 8 with the miniature airplane 6 vvhile thebank attiyoke-shaped gimbal member 9 carrying at its forward endtrunnions III which support the bearing frame for rotation about the'transverse axis perpendicular to the spin axis of the gyroscope. Thegimbal member 9 is supported by axiallyspaced ball bearings, one ofwhich is indicated at 6a, so that the gimbal is free torotate about alongitudinal axis which is perpendicular to the transverse axis definedby the trunnions-I0. With the instrument mounted on the aircraft dashpanel in the usual manner the longitiudinal axis of the gimbal member 9is parallelto orcoincident with the fore and aft axis of the aircraft. f

Due to friction in the gimbal bearings the gyro scope tends to wanderfrom the reference position of the spin axis, which is approximatelyvertical, and for that reason it is necessary to provide an erectionsystem for precessing the gyroscope to the reference position. In orderthat the erecting action will not be dependent for its operation upon anexternal electrical power supply, I prefer to use an eddy currenterection system of the permanent magnet type such as the systemdisclosed and claimed in my copending application Serial No. 636,672,filed December 22, 1945, which is assigned to the same assignee as thepresent invention. The erection system is shown as comprising a rotatingmagnetic field producing element or member II and a cooperating,relatively stationary, current-conducting element or disk I2. The rotaryelement II is formed of a non-magnetic material and is rigidly securedto a gyroscope rotor shaft extension I3 by means of a screw I4 so thatit rotates with the gyroscope.

The rotary member II has embedded therein a series of permanent magnetsI5 which are arranged in concentric circles having a center coincidentwith the axis of rotation of the shaft I3. The permanent magnets I5provide a rotating magnetic field which induces eddy currents in thedisk I2 which currents produce a magnetic field reacting on thegyroscope. The reaction torques, or drag torques, as theymay'be called,are such that they produce no net precession torque on the gyroscopewhen the axis of the disk I 2 is in alignment with the axis of rotationof the member I I. However, if these axes become displaced there is anet torque applied to the gyroscope which causes it to precess to theposition in which theseaxes become realigned.

In order that the disk I2 may be positioned by the force of gravity, itis arranged to be supported by a universal pendulum. The pendulum com-'prises a depending bail I 6 which is pivotally supported on a, second,yoke-shaped gimbal member I! by means of trunnions I8. The gimbal I1 issupported by axially-spaced ball bearings I9a and I 917 for rotationabout an axis coaxial with the axis of rotation of the gimbal member 9.The gimbal members 9 and I1 are arranged in nested relation so that theyare free to rotate relative to each other;

For the purpose of providing means for disabling the erection system attimes when the pendulum I6 does not indicate the true vertical, there isprovided an electroresponsive devicefor increasing the air gapbetweenthe current conducting disk I2 and the permanent magnets I5. In theillustrated arrangement this is accomplished by the provision ofa'bimetal strip 20, oneend of which is rigidly secured to the pendulumor bail I6 by means of a screw 2 I. The opposite end of the bimetalstrip carries the current conducting disk I2, the end being slotted tostraddle a post 22 projecting downwardly from the disk through a centralopening in bail I6. This arrangement permits a small amount of relativemovement between the bimetal strip and the disk to accommodate thewarping movement of the strip. The post 22 is secured to a movable plate23 by means of an adjusting screw 24. The head of the screw 24 issecured to the plate 23 as by staking and the assembly is prevented fromturning by a bent tab 23a which projects upwardly adjacent the sidesurface of bail I6. The plate 23 acts as a stop limiting the upwardmovement of the disk I2 to a normal position where the air gap betweenthe disk and the magnets I5 is a minimum for maximum'normal erectingaction. The normal air gap can be adjusted by screw 24.

The. bimetal strip is initially preloaded or stressed so that disk I2 isbiased upwardly to the position in which plate '23 engages the undersideof bail I6. The preloading is such that normal ambient temperaturevariations do not cause warping of the bimetal strip. The warpingdirection of the lbimetal strip 20 is selected such that when the stripis heated to a, predetermined temperature the lower free end of thestrip moves downwardly carrying with it the current conducting disk I2until the strip engages the upper surface of the bail I6, as shown bythe dotted lines in Figure 2. In order to provide means for causing thebimetal strip 20 to warp downwardly there I is provided an electricheating coil 25 which is wrapped around the central portion of the stripand insulated therefrom by a suitable insulating wrapper'25a. Theheating coil 25 is energized from a suitable powersource indicated bythe plus and ground symbols in Fig. 3 of the drawing. When energized thefree end of the bimetal strip 20 moves downwardly carrying with it thecurrent conducting disk I2 so that the air gap between the disk I2 andthe permanent magnet I5 is greatly increased. As a result of thisincrease in air gap, the erecting torque exerted on thegyroscope'isreduced to a relatively small value so that the erectionsystem is effectively disabled. This disabling of the erection systemmay be controlled either manually or automatically by switching means inthe energization circuit of the bimetal strip heater 25, both'manual andautomatic arrangements being shown in Fig. 3 of the drawing. Referringto Fig. 3it will be noted that there is provided a manually operatedswitch 26 which is connected between one terminal of the heater coil 25and the positive side of the power supply. The switch 26 may for examplebe controlled by means of a knob 26a. located on the front of theinstrument. Thus, under manual operation, wheneverthe pilot wishes todisable the erection system during violent maneuvers to prevent errorsof indication which would otherwise be caused by a swinging of thependulum away from the true vertical position, he closes switch 26energizing the heater coil 25 and causing the bimetallic strip 20 tomove the disk I2 away from the magnets I5. When normal flight is resumedthe switch 26 is opened, the bimetallic strip 20 cools, and the disk 1I2 is returned to its upward operative position.

exerted on the pendulum during turns of the air-..

accessoac and eitherof two electrodes 3| and 32 located at opposite endsof: the capsule. depending on which end of the capsul'eis occupied bythe gl'obule of mercury Thearrangementis such that when the capsule 28is level and is subject to no sideways acceleration force, the mercuryoccupies a center position and does not touch either of the endelectrodescl or 31. However, when the cap- Suleis subjected to asideways centrifugal force the mercury globulecompletes-the circuitbetween electrode 3V- and the electrode 31 or 32 depending onthedirectionthe mercury'has roI-l'edunder the influence of centrifugalforce. In order" that the capsule; 28 may be maintained in a levelposition and be affected only by centrifugal action encountered duringturns, it is mounted on and supported by the rotor bearing frame I ofthe gyroscope so thatit is maintained level by the gyroscope inapositionparallel to the transverse axis of the aircraft. As shown Fig. 3' theend electrodes 3F and :32 are tied together and connected to one side ofthe power supply while the centerel'ectrode 3| connected to the oneterminalioi the coil- 25. Thus whenever a connection is madebetween thecenter electrode 30' and either of the other electrodes 3 l- 01*32, asoccursduring a turn of the aircraft; a circuit is completed energizingtheheater coil 2,5. This-moves the disk I2 away fromthe magnets (-5 sothat acceleration errors do not result in a precession of the gyroscopeaway-from the true reference position.

When the gyroscope motor is initially startedthe gyroscope bearing frameI is usually tilted from the vertical so that" acircuit may becomplot-ed through the centrifugal switch 21. During the initialstarting period it is desirable to have theerectionsystem in operationso that the gyroscope will erect itself to the vertical referenceposition. In order toaccompli's'h this there is provided an auxiliarycutout switch 33 which is connected in serieswiththe" circuit throughthe centrifugal switch 21'. During starting of the gyroscope the switch33 is opened to prevent the operation of the centrifugal switch fromdisabling the erection system. After the gyroscope has come up-to speedand is-ereCted to the vertical position sothat the circuit to thecentrifugal switch is open, the switch 331's then closed so that thecentrifugal switch becomes effective to disable the erection systemduring turns, as described above.

Another factor which may cause the pendulum Hi to be-moved away from thetrue vertical position is the fact thatthe freedom of movement of thependulum is necessarily limited because of structural limitations ofthe"- instrument. Thus for example in: the instrument shown it will beapparent that for dives of the aircraft beyond about 25 degrees, thependulum l6 will be rotated about the trunnion's l8- until itis engagedand displaced by the gimbal member During this condition it is desirablethat the-erection system be disabled and I have shown an arrangement bymeans of which this may be accomplished automatically For thispurpose-there is provided a second pendulum M pivoted at 35 on the framefor rotation about an axis parallel to the transverse action of.theaircraft- Thus the pendulum 34" swings in a manner similar to thependulum Hi. The pendulum: has. attached: thereto camming: surfaces 36which are arranged. to engage and operate a switching member 31 to closeswitch- 38 at dive and climb angles oi the aircraft slightly less'thanthose which cause: the pendulum Hi to engage its stops. As shown in Fig.3 the switch 38- is connected in parallel with the manually operatedswitch 26 and the oentrifiugally' operated. switch 21 and acts toenergize the heater coil: 25- and disable the erection system wheneverthe switch. is closed-by operation of the pendulum 34. The switch 38 isbiased to the open position by spring means not shownso that it isopened. when the pendulum 34 swings back to the center position.

The pendulum 34 also closes switch 38 to disable the erection systemduring accelerations or decelerations of the aircraft exceeding apredetermined value such. as 0.3 g. Such acceleratlons' anddecelerations would, of course, afie'ct' 5 the erecting pendulum. andcause an erection mum-airg'ap' position; In this position the erectionsystem operates in a normal manor subject only to the errors causedbyconditions resulting" in a: swinging of the erecting pendulum Hi, fromthe true vertical position;

An additional: advantage of the permanentmagnet erection system of thetype illustrated is that it-is considerably lighter andimore compactthanan equivalent electromagnetic type Therefore my novel erection cutoutsystem, whichv permelts the use or a permanent magnet system, is

advantageous from this standpoint as well as the fail safeconsideration.

The-automatic erection cutout duri'ngturns affected by operation of thecentrifugal switch 21' and during steep climbs andv dives enacted by thesecond pendulum 34, gives automatic operation of the erection cutout asrequired so that the instrument requires a minimum or attention from thepilot;

Modifications of the particular arrangements which I have disclosedembodying my invention will occurto those skilled in the art, so that Ido not desire my'inventi'on to be limited to the particulai"ari'angeinehts-set forth and I intend in the appended claims to coverall modification which do not depart from the spirit and scope of myinvention. 7

What I claim as new and desire: to secure by Letters Patent of theUniteclstates is:

1. In combination, a universally'mounteu gyroscope, a universallymounted pendulum, an erection' system comprising a magnetic element anda cooperating: current conducting element, one of said elements beingmounted on said gyroscope and; the other'being' mounted on saidpendulum,

means for rotating one of said element's whereby eddy currents-areinduced in-said current" conduc' ting element resulting in an erectintorque on saiugyroscope; and means for reducingsaid erecting tcrque'to arelatively ineiiective value coiiiprising an electroresponsive devicefor increasing the spacing between said elements.

2. In combination with a universally mounted gyroscope, an erectionsystem for precessing the gyroscope to maintain the spin thereof in anapproximately vertical position comprising a magnetic field producingelement and a cooperating current conducting element, one of saidelements being mounted on said gyroscope and the other being mounted ona universal pendulum, means for rotating one of said elements so thatwith a normal spacing between said elements eddy currents are induced inthe current conducting element resulting in a normal erecting torquewhich processes the gyroscope to a predetermined position relative tosaid pendulum, and means for reducing the erecting torque comprising anelectroresponsive device operative when energized to increase thedistance between said elements beyond said normal spacing and means forcontrolling the energization of said electroresponsive device.

3. In combination with a universally mounted gyroscope, an erectionsystem for processing the gyroscope to maintain the spin axis thereof inan approximately vertical position comprising a magnetic field producingelement and a cooperating current conducting element, one of saidelements being mounted on said gyroscope and the other being mounted ona universal pendulum, means for rotating one of said elements so thatwith a normal spacing between said elements eddy currents are induced inthe current conducting element resulting in a normal erecting torquewhich precesses the gyroscope to a predetermined position relative tosaid pendulum, and means for reducing the erecting torque comprising anelectroresponsive device operative when energized to increase thedistance between said elements beyond said normal spacing and'means forcontrolling the energization of said electroresponsive device comprisinga switch and a second pendulum for controlling said switch.

4. In combination, a universally mounted gyroscope, a universallymounted pendulum, an erection system comprising a magnetic element and acooperating current-conducting element, one of said elements beingmounted on said gyroscope and the other being mounted on said pendulum,means for rotating one of said elements whereby eddy currents areinduced in said current-conducting element resulting in an erectingtorque on said gyroscope, and means for reducing said erecting torque toan ineifective value comprising an electroresponsive device forincreasing the spacing between said elements, said electroresponsivedevice comprising a bimetal member arranged to position one of saidelements by a change in curvature of said member and an electric heaterfor heating said bimetal member.

5. In combination, a universally mounted gyroscope, a universallymounted pendulum, an erection system comprising a rotating magneticfield producing element mounted on said gyroscope, a current conductingdisk mounted on said pendulum so as to be movable towards and away fromsaid magnet member to vary the erecting torque exerted on saidgyroscope, electroresponsive means for biasing said erecting disk towardsaid magnetic field producing element and for moving said disk away fromsaid magnetic field producing element, and means for controlling theenergization of said electroresponsive means.

6. In combination a universally mounted gyroscope, a universally mountedpendulum, an erection system comprising a rotating magnetic fieldproducing element mounted on said gyroscope, a bimetal member mounted onsaid pendulum, a current conducting disk carried by said bimetal memberand arranged-to move towards and away from said magnetic field producingelement in response to a change in curvature of said bimetal member, andan electric heater for effecting a change of curvature of said bimetalmember.

7.- In combination, a universally mounted gyroscope, a universallymounted pendulum, an erection system comprising a magnetic element and acooperating current conducting element, one of said elements beingmounted on said gyroscope and the other being mounted on said pendulum,means for rotating one of said elements whereby eddy currents areinduced in said current conducting element resulting in an erectingtorque on said gyroscope, means for reducing said erecting torque to arelatively inefiective value comprising an electroresponsive devicefor'increasing the spacing between said elements, and a centrifugalswitch mounted on and stabilized by'said gyroscope for controlling saidelectroresponsive device.

8. In combination, a universally mounted gyroscope, a universallymounted pendulum, an erection system comprising a magnetic element and acooperating current conducting element, one of said elements beingmounted on said gyroscope and the other being mounted on said pendulum,means for rotating one of said elements whereby eddy currents areinduced in said current conducting element resulting in an erectingtorque on said gyroscope, means for reducing said erecting torque to arelatively ineiiective value comprising an electroresponsive device forincreasing the spacing between said elements, a second pendulum mountedto swing under conditions causing a similar swing of said universalpendulum, and switching means actuated by said second pendulum forcontrolling said electroresponsive device.

9. In combination, a universally mounted gyroscope, a universallymounted pendulum, an erection system comprising a magnetic element and acooperating current conducting element, one of said elements beingmounted on said gyroscope and the other being mounted on said pendulum,means for rotating one of said elements whereby eddy currents areinduced in said current conducting element resulting in an erectingtorque on said gyroscope, means for reducing said erecting torque to arelatively ineffective value comprising an electroresponsive device forincreasing the spacing between said elements, a pair of parallelconnected switching devices connected to control said electroresponsivedevice, a centrifugal switch mounted on and stabilized by said gyroscopecomprising one of said switching devices, and a second pendulum, mountedto swing under conditions causing a similar swing of said universalpendulum, cooperating with a switch comprising the cther of saidswitching devices.

10. In combination, a universally mounted gyroscope, a universallymounted pendulum, an erection system comprising an element mounted onsaid gyroscope and a cooperating torque applying element mounted on saidpendulum, electroresponsive means for disabling said erection system,and an acceleration-responsive, current controlling device mounted onand stabilized by said REFERENCES CITED The following references are ofrecord in the file of th Number is patent:

UNITED STATES PATENTS Name Date 4 Sperry, Jr., et a1. Nov. 14, 1933 SiasJan. 18, 1944 Bosell Oct. 14, 1947

